The purpose of this research is to establish the combined effects of applied load and chemical degradation on failure of articulating surfaces of ultra high molecular weight polyethylene total joint replacement components. Three areas will be studied: 1) the cyclic loading conditions which will cause small defects on and below the articulating surface to propagate and create the surface damage modes generated by fatigue fracture mechanisms observed on retrieved components: 2) the extent of chemical degradation occurring to polyethylene joint components as a function of chemical environment and loading history; and 3) the effect of chemical degradation on surface damage modes generated by fatigue fracture mechanisms. These studies will establish a comprehensive understanding of the integrated chemical, mechanical and structural behavior of polyethylene as used in total joint replacements. The goal is to maximize the long-term performance of polyethylene joint components.